All-photonic quantum networks

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Quantum communication holds promise for unconditionally secure transmission of secret messages and faithful transfer of unknown quantum states. Quantum repeaters are necessary for extending the achievable distance of quantum communication towards the quantum internet. However, all the conventional paradigms required repeater nodes to be equipped with demanding matter quantum memories. Here we show that this requirement is not necessary at all, by presenting ‘all-optical’ quantum communication schemes [1,2]. In particular, these schemes use only optical devices such as linear optical elements, single-photon sources, photon detectors and active feedforwards, that is, without any matter quantum memory. Nonetheless, these schemes can work efficiently as intercity/intercontinental backbone quantum links for the quantum internet.